Fig. 4. Selective inhibition of the reception of either Nodal or Delta signals in one of the four founder cells of the eight-cell embryo. (A) Experimental design showing a vegetal pole view of the eight-cell stage embryo; eight-cell stage embryos were injected with tALK4/5/7 mRNA to block Nodal signal reception, Su(H)^DBM mRNA to block Delta/Notch signal transduction or GFP mRNA as a control. mRNAs were selectively injected into either the A4.1 or the B4.1 blastomere on the right hand side and then analysed for Ci-Bra expression at the early gastrula stage. (B) A graph showing the percentage of embryos (y-axis) with strong or weak Ci-Bra expression in the B8.6 blastomere on the left-(L) or right-(R) hand side of the embryo. Injected RNAs and injected blastomere names are indicated on the x-axis. n=total number of embryos analysed. (C) A representative embryo for each of the treatments.